The present invention relates to a clutching device generally and more specifically to an engine driven apparatus for controllably rotating at least one vehicle mounted accessory at either one of two preselected speed ratios.
The present invention incorporates therein a planetary gear set which is often found in devices of this type used for speed changing applications. The speed changing application is selectively performed by restraining one of either the ring gear, the sun gear, or the planetary gear carrier of the planetary gear set. Cooperating with the planetary gear set is an actuator. Representative of these actuators used in the prior art are electromagnetic clutches or mechanical clutches driven by linear actuators, such as a ball ramp actuator. The electromagnetic clutch often finds use in low torque transmission applications. The ball ramp is used in higher torque transmissions and is susceptible to misalignment, which may result in a reduced life of the drive.
It is an object of this invention to provide a bellows activated underdrive two speed accessory drive that is capable of operating vehicle accessories at full speed or at reduced speed. An advantage of one embodiment of the invention is that the use of thrust bearings is eliminated and plate clutches may be substituted for the main clutching mechanism, such as a cone clutch resulting in light weight and simple construction. In addition, the invention eliminates the need for more complicated means for activating the ball ramp, such as a gear motor or levers.
Accordingly, the invention is directed to a drive having high speed and low speed modes of operation comprising an input shaft, a planetary gear set drivingly connected to the input shaft comprising a sun gear disposed about the shaft, a plurality of planet gears disposed about the sun gear and a ring gear disposed about and engaging the planet gears, and means for preventing the ring gear from rotating during the low speed mode, and an output pulley linked to and rotatable with the planet carrier. The drive further includes clutch means for connecting the output pulley to the input shaft during the high speed mode and for disengaging the output pulley from the input shaft during the low speed mode, and means including a bellows for moving the clutch means into and out from engagement during the high and low speed modes.
Many other objects and purposes of the invention will become clear from the detailed description of the drawings.